Combat vehicles need armor for ballistic protection. One weakness to any armor system is the air passages needed for running engines. For example, armored vehicles often have intake and exhaust vents for supplying air to engine components and other systems. However, if a projectile enters the vent, the projectile can damage the engine or other components or destroy the vehicle. In this application projectiles are considered missiles, artillery rounds, bullets, shrapnel, spall or other debris created by an explosive event. To combat the threat, a grille having a plurality of louvers is commonly fitted to the intake and exhaust vents to prevent projectiles from entering the engine compartment while permitting air to flow between the louvers into the protected area.
A balance must be reached between protection and functionality. While a need exists to supply air for operation and cooling, there is also a need to protect the occupants of the vehicle as well as allow the vehicle to perform a given mission. Ballistic grilles are thus used to provide protection as well as airflow. The required openings for air flow make grilles inherently difficult to protect. As a result, grilles are traditionally not as well protected as the rest of vehicles armor.
There have been many types of approaches to protecting the intake and exhaust openings. Grilles with bars or louvers may slow or catch a threat, but because they are open, they may not fully stop a penetrator, or small fragments may break off and pass through the openings to impact crew or components behind the grille. Improving airflow, while providing improved ballistic protection, is always difficult.
Over the past decade, armor engineers have discovered/developed several concepts which improve grille aerodynamics and ballistics. Methods of defeating ballistic threats have focused in the past on the shape of the grille or increasing the weight of the grille. A common approach to reducing armor weight is through ceramics. Conventional armors use this approach; body armor uses hard ceramic in front with tough high strength fibers behind. Vehicle armors use hardened steel outer layers or ceramic on a tough middle or structural layer like aluminum or a softer more ductile steel and then inboard a tough high strength fiber layer. In conventional armor these layers are flat plates.
Grille armor has consisted of louvers, typically in a chevron or S shape. Made of aluminum or steel, the louvers are spaced to provide a circuitous open path that air can flow through. Projectiles that fly in a straight line are stopped by contact with the louvers. However, thick louvers block airflow or create stagnation points which affect engine performance.
All known grilles use the same materials through their full height. Some use laminates of different material as bars, but they go through the full thickness of the grille. The earlier designs have not worked to maximize the airflow while maintaining protection. Air flow is affected by spacing between the bars, width of the bars, and dimensions along the width of the bars.
An optimized ballistic grille must use openings in these elements to allow air flow. The greater the opening size, the better the flow, but the greater the challenge to ballistic protection. As such, there is a need for maintaining the protective ability of the grille while improving the airflow through the circuitous path. Similarly, there is a need for improving the protective ability of the grille while reducing or maintaining the weight and profile of the grill. The objective is to create a new grille which improves ballistic protection, reduces pressure drop and maintains flow volume over the existing steel bent bar grille.